Recent wetting trend over Taklamakan and Gobi Desert dominated by internal variability

The Taklamakan and Gobi Desert (TGD) region has experienced a pronounced increase in summer precipitation, including high-impact extreme events, over recent decades. Despite identifying large-scale circulation changes as a key driver of the wetting trend, understanding the relative contributions of internal variability and external forcings remains limited. Here, we approach this problem by using a hierarchy of numerical simulations, complemented by diverse statistical analysis tools. Our results offer strong evidence that the atmospheric internal variations primarily drive this observed trend. Specifically, recent changes in the North Atlantic Oscillation have redirected the storm track, leading to increased extratropical storms entering TGD and subsequently more precipitation. A clustering analysis further demonstrates that these linkages predominantly operate at the synoptic scale, with larger contributions from large precipitation events. Our analysis highlights the crucial role of internal variability, in addition to anthropogenic forcing, when seeking a comprehensive understanding of future precipitation trends in TGD.


Fig S2 .
Fig S2.Linear trends of summer precipitation.Linear trends of summer precipitation (units: mm d -1 dec -1 ) based on NOAA/Climate Prediction Center (CPC) dataset (a) and different model experiments with their name listed in top-left corner (b-h).Stippling in (a)-(h) indicates regions where the trends are statistically significant at the 95% confidence level.Colored circles in (a) are results based on the Global Historical Climatology Network (GHCN) station records.The bigger circles indicate the trends are statistically significant at the 95% confidence level.The Taklamakan and Gobi Desert (TGD) region is delineated by the black rectangle.The gray isoline represents the 2,000-m contour of surface elevation.Source data are provided as a Source Data file.

Fig. S4 .
Fig. S4.Composite precipitation trend based on variability analogue ensembles.a, Linear trends of summer precipitation based on the variability analogue ensembles using 5-year segments.Stippling indicates regions where the trends are statistically significant at the 95% confidence level.The Taklamakan and Gobi Desert (TGD) region is delineated by the black rectangle.The gray isoline represents the 2,000-m contour of surface elevation.b, Time series of the summer precipitation averaged over TGD region based on the variability analogue ensembles (blue) and NOAA/Climate Prediction Center (CPC) dataset (black).The light blue shading denotes the spread among the respective ensembles.The mean, linear trend, and the correlation coefficient with the CPC dataset are shown for variability analogue ensembles using 5-year segments.Source data are provided as a Source Data file.

Fig. S5 .
Fig. S5.Empirical Orthogonal Function (EOF) analysis of 200 hPa eddy kinetic energy (EKE) over the North Atlantic.(upper panel), The first and second leading mode pattern of the EOF analysis.Contours denote the 20-year mean EKE (units: m 2 s -2 ).(bottom panel), The associated principal component (PC1) time series of the first and second leading EOF during 2000-2019.Source data are provided as a Source Data file.

Fig. S8 .
Fig. S8.Mid-level (500 hPa) large-scale circulation patterns.Composite of mid-troposphere (500 hPa) geopotential height anomalies overlaid with horizontal winds for the three clusters based on (a-c) the Fifth Generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5), (d-f) iCMIP experiment, and (g-i) nAMIP experiment.The Taklamakan and Gobi Desert (TGD) region is delineated by the black rectangle.The gray isoline represents the 2,000-m contour of surface elevation.Source data are provided as a Source Data file.

Fig. S9 .
Fig. S9.Low-level (700 hPa) large-scale circulation patterns.Composite of near-surface (700 hPa) moisture flux divergence anomalies overlaid with 700 hPa moisture flux for the three clusters based on (a-c) the Fifth Generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5), (d-f) iCMIP experiment, and (g-i) nAMIP experiment.The Taklamakan and Gobi Desert (TGD) region is delineated by the black rectangle.The gray isoline represents the 2,000-m contour of surface elevation.Gray areas indicate region where the 700 hPa surface lies below ground level.Source data are provided as a Source Data file.

Fig. S10 .
Fig. S10.Eddy kinetic energy (EKE) composite.Composite EKE anomalies for the three clusters based on the Fifth Generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5).Dots in (a)-(c) indicate regions where the anomalies are statistically significant at the 95% confidence level.The Taklamakan and Gobi Desert (TGD) region is delineated by the black rectangle.The gray isoline represents the 2,000-m contour of surface elevation.Source data are provided as a Source Data file.